This recipe links to this Amylase product on Amazon: https://amzn.to/3FOHpid

The product page doesn't go into detail, but the Q&A on similar products state that it is Alpha-amylase.

For the record, the first time I attempted this recipe the bread did not turn out. It was overly developed, and after fully baking was very sticky and slimy. Other research I did made me conclude that 4g of this Amylase Enzyme powder is probably way too much. It should probably have been 0.4g. I will test again in the future.